1. Field of the Invention
The invention relates to edge card connectors by which flexible electronic circuitry, including lengths of flat flexible cable, are interconnected with other electrical circuit components.
2. Background Art
The prior art teaches use of edge card connectors by which to provide an electrical interconnection between a rigid, planar printed circuit board and another electrical circuit component, to which the edge card connector is itself mounted. A typical edge card connector includes a connector housing having an elongate main slot within which to receive a mating edge of the circuit board. The connector housing further typically includes a plurality of secondary slots intersecting the housing""s main slot. A plurality of spring contacts or terminals disposed in the secondary slots project slightly into the main slot of the housing such that, upon insertion of the mating edge of the circuit board into the main slot, the spring contacts resiliently engage respective conductive traces or plated contacts defined on one side of the circuit board.
It has recently become increasingly desirable to provide electrical assemblies which employ a flexible substrates, for example, to improve assembly packaging, or to provide integrated electrical assemblies incorporating a plurality of permanently (and flexibly) discrete, interconnected electronic modules. A need has thus arisen for a connector and method for interconnecting a flexible-substrate electrical circuit component, including lengths of flat flexible cable, to another electrical circuit component using conventional edge card connectors.
In response, for example, U.S. Pat. No. 4,808,113 teaches an adapter which, when inserted into the main slot of an edge card connector, defines a reduced-width slot within which to receive the relatively-thinner end of a length of flat flexible cable. The flat flexible cable is thereafter retained in the edge card connector by virtue of the mechanical engagement of the edge card connector""s spring contacts with the cable""s exposed electrically-conductive traces. Such mechanical engagement necessarily limits the xe2x80x9cpull-outxe2x80x9d or retention force that may be achieved using this prior art design. Moreover, because the spring contacts perform the functions of both mechanical retention and electrical conduction, a less reliable interconnection connection is achieved that may particularly impact certain relatively-high-current electrical applications, as might be found in an automotive context.
It is an object of the invention to provide an edge connector for use with flexible circuitry featuring that overcomes the aforementioned deficiencies of the prior art.
Under the invention, an adapter is provided for interconnecting flexible circuitry with an edge card connector, wherein the flexible circuitry includes a thin, flexible substrate having an edge, a first face, and a second face, and a plurality of electrical conductors on a first face of the substrate which extend towards the edge of the substrate. The adapter includes a thin, substantially-flat, rigid projection having an edge, an upper surface and a lower surface; and means, such as an adhesive layer or a mechanical interlock, for securing the second face of the substrate to the upper surface of the projection. The substrate is arranged to wrap around the edge with the substrate""s second face adjacent to the lower surface of the projection.
In accordance with another feature of the invention, flexible circuitry for interconnection with an edge card connector includes a thin, flexible substrate having an edge, a first face, a second face, and a plurality of electrical conductors defined on the first face which extend towards the edge of the substrate. The flexible circuitry also includes an adapter having a thin, substantially-flat, rigid projection with an edge, an upper surface and a lower surface, wherein a first portion of the substrate proximate to the edge of the substrate is wrapped around the edge of the projection such that a second face of the flexible substrate is positioned adjacent to both the upper surface of the projection and the lower surface of the projection.
In a preferred embodiment, the second face of the flexible circuitry""s substrate is secured to the upper surface of the projection, for example, by an adhesive interposed between the second face of the substrate and the upper surface of the projection, or by virtue of a suitable mechanical interlock, for example, by passing the edge of the flexible circuitry""s substrate back through a slot formed in the adapter""s projection. Preferably, the electrical conductors on the flexible circuitry terminate a predetermined distance from the edge of the substrate, for example, at the point where the substrate defines a bend radius as the substrate wraps around the edge of the projection.
In accordance with the invention, a method is provided for adapting thin, flexible circuitry for interconnection with an edge card connector, wherein the flexible circuitry includes a plurality of exposed electrical conductors on a first face proximate to, but, preferably, positioned a predetermined distance away from, a first edge. The method includes wrapping a first portion of the flexible circuitry proximate to its first edge around a second edge defined on a thin, substantially-flat, rigid projection of an adapter, such that a second face of the flexible circuitry is positioned adjacent to both an upper surface of the projection and a lower surface of the projection. The method further preferably includes securing the first portion of the flexible circuitry to the adapter""s projection, for example, by bonding the second face of the flexible circuitry to the upper surface of the projection, or by mechanically interlocking the first portion of the flexible circuitry with the adapter.
In accordance with another feature of the invention, an exemplary method includes terminating the exposed electrically-conductive layers or traces on the on the first portion of the flexible circuitry at the point where the first portion begins to wrap around the adapter""s projection.
By wrapping the flexible substrate around the projecting edge of the adapter and subsequently attaching the adapter to the edge card connector, the invention advantageously improves the retention force characteristic of the resulting connector assembly while otherwise further facilitating initial insertion of the end of the flexible circuitry into the edge card connector. When the projecting edge of the adapter is further formed of a thermally-conductive material, the invention further advantageously provides for heat transfer away from the flexible circuit/edge card connector through the adapter, for example, in higher current applications.
Other objects, features and advantages of the present invention are readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.